Many printers do not have a visible paper supply. The paper is stored in drawers or trays with the contents out of sight. When the last piece of paper is used, the printer stops printing, and an indicator turns on to indicate that the printer needs paper. Alternatively, a small Liquid Crystal Display (LCD) screen displays a message that paper is out. To implement such alert systems, sensors are used to detect when a resource is depleted. For instance, the paper tray would include an electrical or electromechanical sensor to detect when the paper tray is empty. The sensor, upon detecting that the resource is close to or at depletion, would signal the printer processor and the printer processor would, in response, enable the paper out indicator in the printer.
While the printer provides an indication of the out of paper condition, many people never notice that the printer has stopped and requires paper. Instead, they simply take their output and leave. Sometimes, their jobs are not complete, because the printer runs out of paper in the middle of the job. When someone finally realizes that the printer needs paper and replenishes the supply, the printer completes the previous job. What is needed is a printer that provides a more noticeable out of paper indicator that encourages users to replenish the paper supply and helps prevent a user from unknowingly walking away with an incomplete print job.